Casting mold material and copper alloy material

ABSTRACT

A casting mold material used when casting a metal material includes, as a composition: Cr within a range of 0.3 mass % or more and 0.7 mass % or less; Zr within a range of 0.025 mass % or more and 0.15 mass % or less; Sn within a range of 0.005 mass % or more and 0.04 mass % or less; P within a range of 0.005 mass % or more and 0.03 mass % or less; and a balance consisting of Cu and inevitable impurities, in which a Zr content [Zr] (mass %) and a P content [P] (mass %) have a relationship of [Zr]/[P]≥5, and a Sn content [Sn] (mass %) and a P content [P] (mass %) have a relationship of [Sn]/[P]≤5.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a U.S. National Phase Application under 35 U.S.C. § 371 of International Patent Application No. PCT/JP2018/036324, filed Sep. 28, 2018, and claims the benefit of priority to Japanese Patent Application No. 2017-223760, filed Nov. 21, 2017, all of which are incorporated herein by reference in their entirety. The International Application was published in Japanese on May 31, 2019 as International Publication No. WO/2019/102716 under PCT Article 21(2).

FIELD OF THE INVENTION

The present invention relates to a casting mold material used when casting a metal material such as steel, aluminum, and copper, and a copper alloy material suitable for a member used in a high-temperature environment, such as the casting mold material described above.

BACKGROUND OF THE INVENTION

In the related art, a casting mold material used when casting a metal material such as steel, aluminum, and copper is required to be excellent in properties such as high-temperature strength to withstand large thermal stress, high-temperature elongation to withstand a severe thermal fatigue environment, wear resistance (hardness) at high temperature, and thermal conductivity.

A Cu—Cr—Zr alloy such as C18150 has excellent heat resistance and conductive property (thermal conductivity), and thus is used as a material such as a casting mold material which is used in an environment at high temperature, as shown in Japanese Patent No. 5590990 and Japanese Unexamined Patent Application, First Publication No. S58-107460.

The Cu—Cr—Zr alloy described above is usually produced by a production step in which a Cu—Cr—Zr alloy ingot is subjected to plastic working, a solution treatment, for example, at a holding temperature of 950° C. to 1050° C. for a holding time of 0.5 to 1.5 hours and an aging treatment, for example, at a holding temperature of 400° C. to 500° C. for a holding time of 2 to 4 hours, and finally a predetermined shape is obtained by machining.

Thus, the Cu—Cr—Zr alloy has improve strength and conductive property (thermal conductivity) by dissolving Cr and Zr in a Cu matrix by solution treatment and finely dispersing a Cr precipitate (Cu—Cr) or a Zr precipitate (Cu—Zr) by an aging treatment.

Technical Problem

In recent years, a casting mold material that can be used even in a severe environment is required due to a demand such as an increase in the number of kinds of alloy to be cast or cost reduction by extending the life of the mold.

More specifically, depending on the kinds of alloy, the temperature of a molten metal injected into a mold may be set high, and high-temperature strength superior to that of the related art is required. Also, in the mold, the temperature near a molten metal surface tends to increase locally. Therefore, a dispersion state of the precipitate changes in a region where the temperature is high, and local decrease in strength and improvement of conductive property (improvement of thermal conductivity) occur in the mold, and a cooling state becomes unstable. Thus, there was a concern that casting could not be performed stably.

The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a casting mold material which is excellent in high-temperature strength, prevents local decrease in strength and improvement of conductive property (thermal conductivity) from occurring even in the case of being used under high-temperature conditions, and is capable of stably performing casting, and a copper alloy material suitable for the casting mold material.

SUMMARY OF THE INVENTION Solution to Problem

In order to solve the above problems, a casting mold material of the present invention used when casting a metal material includes, as a composition: Cr within a range of 0.3 mass % or more and 0.7 mass % or less; Zr within a range of 0.025 mass % or more and 0.15 mass % or less; Sn within a range of 0.005 mass % or more and 0.04 mass % or less; P within a range of 0.005 mass % or more and 0.03 mass % or less; and a balance consisting of Cu and inevitable impurities, in which a Zr content [Zr] (mass %) and a P content [P] (mass %) have a relationship of [Zr]/[P]≥5, and a Sn content [Sn](mass %) and a P content [P] (mass %) have a relationship of [Sn]/[P]≤5.

In the casting mold material having this composition, Cr is included within the range of 0.3 mass % or more and 0.7 mass % or less and Zr is included within the range of 0.025 mass % or more and 0.15 mass % or less. Therefore, a fine precipitate can be precipitated by an aging treatment, and strength and electrical conductivity can be improved.

In addition, Sn is included within the range of 0.005 mass % or more and 0.04 mass % or less. Therefore, strength can be improved by solid solution strengthening.

Thus, P is included within the range of 0.005 mass % or more and 0.03 mass % or less. Therefore, a Zr—P compound or a Cr—Zr—P compound is formed by reacting with Zr and Cr. These Zr—P compound and the Cr—Zr—P compound are stable even at high temperature. Therefore, even in the case of being used under high-temperature conditions, it is possible to prevent local decrease in strength and improvement of conductive property (thermal conductivity) from occurring. In addition, crystal grain size can be prevented from becoming coarse, and high-temperature strength can be improved.

Furthermore, the Zr content [Zr] (mass %) and the P content [P] (mass %) have the relationship of [Zr]/[P]≥5. Therefore, even when the Zr—P compound or the Cr—Zr—P compound is formed, the number of the Cu—Zr precipitates contributing to strength improvement is secured, and strength improvement can be achieved.

In addition, the Sn content [Sn] (mass %) and P content [P] (mass %) have the relationship of [Sn]/[P]≤5. Therefore, the decrease in electrical conductivity due to a solid solution of Sn can be compensated for by an increase in electrical conductivity due to the formation of the Zr—P compound or the Cr—Zr—P compound, and excellent conductive property (thermal conductivity) can be secured.

The casting mold material of the present invention may further include 0.005 mass % or more and 0.03 mass % or less of Si. In this case, the strength can be further improved by solid solution strengthening due to dissolving of Si in the copper matrix.

In the casting mold material of the present invention, a total content of elements of Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti is preferably 0.03 mass % or less. In this case, the total content of elements of Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti, which are impurity elements, is limited to 0.03 mass % or less. Therefore, it is possible to prevent a conductive property (thermal conductivity) from decreasing.

In the casting mold material of the present invention, electrical conductivity is preferably higher than 70% IACS. In this case, the electrical conductivity is higher than 70% IACS. Therefore, Cr precipitates and Zr precipitates are sufficiently dispersed, and the Zr—P compound or the Cr—Zr—P compound is formed. Accordingly, even in the case of being used under high-temperature conditions, it is possible to prevent local decrease in strength and improvement of conductive property (thermal conductivity) from occurring. In addition, crystal grain size can be prevented from becoming coarse, and high-temperature strength can be improved.

In the casting mold material of the present invention, Vickers hardness is preferably 115 Hv or more. In this case, the Vickers hardness is 115 Hv or more. Therefore, sufficient hardness is obtained, and it is possible to prevent deformation from occurring during use and use the material favorably as a casting mold material.

In the casting mold material of the present invention, an average crystal grain size after performing heat treatment at 1000° C. for 30 minutes is preferably 100 μm or smaller. In this case, even when used under high-temperature conditions, the crystal grain size is prevented from becoming coarse, and a decrease in strength can be prevented from occurring. In addition, propagation speed of a fracture can be suppressed and a large breakage due to thermal stress or the like can be prevented from occurring.

A copper alloy material of the present invention includes, as a composition: Cr within a range of 0.3 mass % or more and 0.7 mass % or less; Zr within a range of 0.025 mass % or more and 0.15 mass % or less; Sn within a range of 0.005 mass % or more and 0.04 mass % or less; P within a range of 0.005 mass % or more and 0.03 mass % or less; and a balance consisting of Cu and inevitable impurities, in which a Zr content [Zr](mass %) and a P content [P] (mass %) have a relationship of [Zr]/[P]≥5, a Sn content [Sn] (mass %) and a P content [P] (mass %) have a relationship of [Sn]/[P]≤5; and electrical conductivity after performing a solution treatment at 1015° C. for 1.5 hours and then performing an aging treatment at 475° C. for 3 hours is higher than 70% IACS.

In the copper alloy material having the composition, Cr precipitates and Zr precipitates are sufficiently dispersed, and a Zr—P compound or a Cr—Zr—P compound is formed. Therefore, even in the case of being used under high-temperature conditions, it is possible to prevent local decrease in strength and improvement of conductive property (thermal conductivity) from occurring. In addition, crystal grain size can be prevented from becoming coarse, and high-temperature strength can be improved.

The copper alloy material of the present invention may further include 0.005 mass % or more and 0.03 mass % or less of Si. In this case, the strength can be further improved by solid solution strengthening due to dissolving of Si in the copper matrix.

In the copper alloy material of the present invention, a total content of elements of Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti is preferably 0.03 mass % or less. In this case, the total content of elements of Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti, which are impurity elements, is limited to 0.03 mass % or less. Therefore, it is possible to prevent a conductive property (thermal conductivity) from decreasing.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a casting mold material which is excellent in high-temperature strength, prevents local decrease in strength and improvement of conductive property (thermal conductivity) from occurring even in the case of being used under high-temperature conditions, and is capable of stably performing casting, and a copper alloy material suitable for the casting mold material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating a method of producing a casting mold material according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing positions where Vickers hardness is measured in an example.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a casting mold material and a copper alloy material according to an embodiment of the present invention will be described.

The casting mold material is used as a continuous casting mold when casting continuously a metal material such as steel, aluminum, and copper. In addition, the copper alloy material is used as a material for the casting mold material described above.

The casting mold material and the copper alloy material include, as a composition: Cr within a range of 0.3 mass % or more and 0.7 mass % or less; Zr within a range of 0.025 mass % or more and 0.15 mass % or less; Sn within a range of 0.005 mass % or more and 0.04 mass % or less; P within a range of 0.005 mass % or more and 0.03 mass % or less; and a balance consisting of Cu and inevitable impurities.

Then, a Zr content [Zr] (mass %) and a P content [P] (mass %) have a relationship of [Zr]/[P]≥5.

In addition, a Sn content [Sn] (mass %) and a P content [P] (mass %) have a relationship of [Sn]/[P]≤5.

The casting mold material and the copper alloy material may include Si within a range of 0.005 mass % or more and 0.03 mass % or less.

In the casting mold material and the copper alloy material, a total content of elements of Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti may be 0.03 mass % or less.

In the casting mold material, electrical conductivity is preferably higher than 70% IACS.

In the casting mold material, Vickers hardness is preferably 115 Hv or more.

In the casting mold material, an average crystal grain size after performing heat treatment at 1000° C. for 30 minutes is preferably 100 μm or smaller.

In the copper alloy material, electrical conductivity after performing a solution treatment at 1015° C. for 1.5 hours and then performing an aging treatment at 475° C. for 3 hours is preferably higher than 70% IACS.

The reason why the component composition and characteristics of the casting mold material and the copper alloy material according to the present embodiment are Defined as Described Above Will be Described Below.

(Cr: 0.3 mass % or more and 0.7 mass % or less)

Cr is an element having an effect of improving strength (hardness) and electrical conductivity by finely precipitating Cr precipitates (for example, Cu—Cr) in the crystal grains of a matrix by the aging treatment. In the case where the Cr content is less than 0.3 mass %, the amount of precipitation becomes insufficient in the aging treatment, and the effect of improving the strength (hardness) and the electrical conductivity may not be sufficiently obtained. In addition, in the case where the Cr content is more than 0.7 mass %, a relatively coarse Cr crystallized product may be formed.

Based on the above, in the present embodiment, the Cr content is set within the range of 0.3 mass % or more and 0.7 mass % or less. In order to reliably obtain the effects described above, a lower limit of the Cr content is preferably set to 0.4 mass % or more, and an upper limit of the Cr content is preferably set to 0.6 mass % or less.

(Zr: 0.025 Mass % or More and 0.15 Mass % or Less)

Zr is an element having an effect of improving strength (hardness) and electrical conductivity by finely precipitating Zr precipitates (for example, Cu—Zr) at a grain boundary of a matrix by the aging treatment. In the case where the Zr content is less than 0.025 mass %, the amount of precipitation becomes insufficient in the aging treatment, and the effect of improving the strength (hardness) and the electrical conductivity may not be sufficiently obtained. In addition, in the case where the Zr content is more than 0.15 mass %, the electrical conductivity may decrease, or the Zr precipitate may be coarsened and the effect of improving the strength may not be obtained.

Based on the above, in the present embodiment, the Zr content is set within the range of 0.025 mass % or more and 0.15 mass % or less.

In order to reliably obtain the effects described above, a lower limit of the Zr content is preferably set to 0.05 mass % or more, and an upper limit of the Zr content is preferably set to 0.13 mass % or less.

(Sn: 0.005 Mass % or More and 0.04 Mass % or Less)

Sn is an element having an effect of improving strength by being dissolved in a copper matrix. In addition, Sn also has an effect of increasing a peak temperature of softening characteristics. In the case where the Sn content is less than 0.005 mass %, the effect of improving the strength (hardness) by being dissolved may not be sufficiently obtained. In addition, in the case where the Sn content is more than 0.04 mass %, the conductive property (thermal conductivity) may decrease.

Based on the above, in the present embodiment, the Sn content is set within the range of 0.005 mass % or more and 0.04 mass % or less.

In order to reliably obtain the effects described above, a lower limit of the Sn content is preferably set to 0.01 mass % or more, and an upper limit of the Sn content is preferably set to 0.03 mass % or less.

(P: 0.005 Mass % or More and 0.03 Mass % or Less)

P is an element having effects of stably forming a Zr—P compound or a Cr—Zr—P compound at high temperature, together with Zr and Cr, and preventing the crystal grain size in a high-temperature state from becoming coarse. In the case where the P content is less than 0.005 mass %, there are concerns that the Zr—P compound or the Cr—Zr—P compound may not be formed sufficiently, and the effect of preventing the crystal grain size in a state of from becoming coarse at high temperature may not be obtained sufficiently. In addition, in the case where the P content is more than 0.03 mass %, there are concerns that the Zr—P compound or the Cr—Zr—P compound may be excessively formed, the number of the Cu—Zr precipitates contributing to strength improvement may be insufficient, and strength improvement cannot be achieved.

Based on the above, in the present embodiment, the P content is set within the range of 0.005 mass % or more and 0.03 mass % or less.

In order to reliably obtain the effects described above, a lower limit of the P content is preferably set to 0.008 mass % or more, and an upper limit of the P content is preferably set to 0.020 mass % or less.

([Zr]/[P]: More than 5)

As described above, P reacts with Zr to form a Zr—P compound or Cr—Zr—P compound that is stable at high temperature. In the case where a ratio [Zr]/[P] between the Zr content [Zr] (mass %) and the P content [P] (mass %) is 5 mass % or less, there are concerns that the quantity of Zr to P may decrease and the Zr—P compound or the Cr—Zr—P compound may be formed; accordingly, the number of the Cu—Zr precipitates contributing to strength improvement may be insufficient, and strength improvement cannot be achieved.

Based on the above, in the present embodiment, the ratio [Zr]/[P] between the Zr content and the P content is set to be more than 5.

In order to reliably ensure the number of Cu—Zr precipitates contributing to strength improvement, it is preferable that the ratio [Zr]/[P] between the Zr content and the P content be 7 or more.

([Sn]/[P]: 5 or Less)

As described above, Sn decreases the conductive property (thermal conductivity) by being dissolved in the copper matrix. On the other hand, P improves the conductive property (thermal conductivity) by forming the Zr—P compound or the Cr—Zr—P compound. In the case where the ratio [Sn]/[P] between the Sn content [Sn](mass %) and the P content [P] (mass %) is more than 5, there are concerns that the amount of Sn to P increases, and a decrease in the conductive property (thermal conductivity) due to solid solution of Sn may not be compensated for by the improvement in the conductive property (thermal conductivity) due to the formation of the Zr—P compound or the Cr—Zr—P compound.

Based on the above, in the present embodiment, the ratio [Sn]/[P] between the Sn content and the P content is set to be 5 or less.

In order to reliably improve the conductive property (thermal conductivity), the ratio [Sn]/[P] between the Sn content and the P content is preferably 3 or less.

(Si: 0.005 Mass % or More and 0.03 Mass % or Less)

Sn is an element having an effect of improving strength by being dissolved in a copper matrix, and may be added as needed. In the case where the Si content is less than 0.005 mass %, the effect of improving the strength (hardness) by being dissolved may not be sufficiently obtained. In addition, in the case where the Si content is more than 0.03 mass %, the conductive property (thermal conductivity) may decrease.

Based on the above, in the present embodiment, in the case where Si is added, it is preferable that the Si content be set within a range of 0.005 mass % or more and 0.03 mass % or less.

In order to reliably obtain the effects described above, a lower limit of the Si content is preferably set to 0.010 mass % or more, and an upper limit of the Si content is preferably set to 0.025 mass % or less.

(Total Content of Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti: 0.03 Mass % or Less)

Elements such as Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti can significantly decrease the conductive property (thermal conductivity). Therefore, in order to reliably maintain a high conductive property (thermal conductivity), it is preferable to limit the total content of Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti to 0.03 mass % or less. Furthermore, it is preferable to limit the total content of Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti to 0.01 mass % or less.

(Other Inevitable Impurities)

Examples of other inevitable impurities other than Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti described above include B, Ag, Ca, Te, Sr, Ba, Sc, Y, Ti, Hf, V, Nb, Ta, Mo, W, Re, Ru, Os, Se, Rh, Ir, Pd, Pt, Au, Cd, Ga, In, Li, Ge, As, Sb, Tl, Pb, Be, N, H, Hg, Tc, Na, K, Rb, Cs, Po, Bi, lanthanoid, O, S, and C. Since these inevitable impurities may decrease the conductive property (thermal conductivity), the total amount thereof is preferably 0.05 mass % or less.

(Electrical Conductivity: Higher than 70% IACS)

In the case where the electrical conductivity of the casting mold material is higher than 70% IACS, Cr precipitates and Zr precipitates are sufficiently dispersed, and the Zr—P compound or the Cr—Zr—P compound is formed. Accordingly, the strength and the conductive property (thermal conductivity) are improved, and even in the case of being used under high-temperature conditions, the crystal grain size can be prevented from becoming coarse.

Based on the above, the electrical conductivity of the casting mold material is set to be higher than 70% IACS. The electrical conductivity of the casting mold material is further preferably set to be 75% IACS or more.

(Vickers Hardness: 115 Hv or More)

In the case where the Vickers hardness of the casting mold material is 115 Hv or more, sufficient hardness can be secured and deformation during use can be suppressed.

Based on the above, in the casting mold material of the present embodiment, the Vickers hardness is set to 115 Hv or more. The Vickers hardness of the casting mold material is further preferably set to 130 Hv or more.

(Average Crystal Grain Size after Performing Heat Treatment at 1000° C. for 30 Minutes: 100 μm or Smaller)

As described above, when stably forming the Zr—P compound or the Cr—Zr—P compound at high temperature, the crystal grain size in a high-temperature state can be prevented from becoming coarse. Therefore, when limiting the average crystal grain size to 100 μm or smaller after performing heat treatment at 1000° C. for 30 minutes, the Zr—P compound or the Cr—Zr—P compound can be stably formed at high temperature. Therefore, it is possible to prevent the strength from decreasing when used under high-temperature conditions. In addition, propagation speed of a fracture can be suppressed and a large breakage due to thermal stress or the like can be prevented from occurring.

Based on the above, in a casting mold material, the average crystal grain size after performing the heat treatment at 1000° C. for 30 minutes is set to 100 μm or smaller. In the casting mold material, an average crystal grain size after performing the heat treatment at 1000° C. for 30 minutes is preferably set to 5 μm or larger and 70 μm or smaller.

(Electrical Conductivity after Aging Treatment: Higher than 70% IACS)

In the copper alloy material, in the case where electrical conductivity after performing a solution treatment at 1015° C. for 1.5 hours and then performing an aging treatment at 475° C. for 3 hours is higher than 70% IACS, Cr precipitates and Zr precipitates are sufficiently dispersed, and the Zr—P compound or the Cr—Zr—P compound is formed. Accordingly, even in the case of using the copper alloy material under high-temperature conditions, it is possible to prevent local decrease in strength or improvement of conductive property (thermal conductivity) from occurring. In addition, a crystal grain size can be prevented from becoming coarse, and high-temperature strength can be improved.

Based on the above, in the copper alloy material, electrical conductivity after performing a solution treatment at 1015° C. for 1.5 hours and then performing an aging treatment at 475° C. for 3 hours is set to be higher than 70% IACS. In the copper alloy material, electrical conductivity after performing the solution treatment at 1015° C. for 1.5 hours and then performing the aging treatment at 475° C. for 3 hours is further preferably higher than 75% IACS.

Next, a method of producing a casting mold material according to an embodiment of the present invention will be described with reference to a flowchart of FIG. 1.

(Melting and Casting Step S01)

First, a copper raw material formed of oxygen-free copper with a copper purity of 99.99 mass % or higher is charged into a carbon crucible and melted using a vacuum melting furnace to obtain molten copper. Next, the additive elements described above are added to the obtained molten metal so as to have a predetermined concentration, and the components are formulated to obtain molten copper alloy.

As raw materials for the additive elements Cr, Zr, Sn, and P, for example, it is preferable that a Cr raw material with a purity of 99.9 mass % or higher be used, a Zr raw material with a purity of 99 mass % or higher be used, a Sn material with a purity of 99.9 mass % or higher be used, and P be used as a mother alloy with Cu. Si may be added as needed. In the case where Si is added, it is preferable to use a mother alloy with Cu.

Then, the molten copper alloy is poured into a mold to obtain an ingot.

(Homogenization Step S02)

Next, heat treatment is performed to homogenize the obtained ingot. Specifically, the ingot is subjected to a homogenization treatment in an air atmosphere under conditions of 950° C. or higher and 1050° C. or lower for 1 hour or longer.

(Hot Working Step S03)

Next, hot rolling is performed at a processing rate of 50% or higher and 99% or less in a temperature range of 900° C. or higher and 1000° C. or lower to obtain a rolled material. A method of hot working may be hot forging. Immediately after the hot working, cooling is performed by water cooling. The copper alloy material is produced by such steps.

(Solution Treatment Step S04)

Next, the rolled material obtained in the hot working step S03 is subjected to a solution treatment by performing heat treatment under conditions of 920° C. or higher and 1050° C. or lower and 0.5 hours or longer and 5 hours or shorter. The heat treatment is performed in, for example, an air or inert gas atmosphere, and cooling after the heating is performed by water cooling.

(Aging Treatment Step S05)

Next, after the solution treatment step S04, an aging treatment is performed to finely precipitate precipitates such as Cr precipitates and Zr precipitates. As a result, the electrical conductivity after the solution treatment becomes higher than 70% IACS. The aging treatment is performed, for example, under conditions of 400° C. or higher and 530° C. or lower for 0.5 hours or longer and 5 hours or shorter.

The method of heat treatment during the aging treatment is not particularly limited, and is preferably carried out in an inert gas atmosphere. In addition, a method of cooling after the heat treatment is not particularly limited, and is preferably carried out by water cooling.

The casting mold material is produced by such steps.

In the casting mold material and the copper alloy material which have the composition as described above, Cr is included within the range of 0.3 mass % or more and 0.7 mass % or less and Zr is included within the range of 0.025 mass % or more and 0.15 mass % or less. Therefore, a fine precipitate can be precipitated by an aging treatment, and strength and electrical conductivity can be improved.

In addition, Sn is included within the range of 0.005 mass % or more and 0.04 mass % or less. Therefore, strength can be improved by solid solution strengthening.

Thus, P is included within the range of 0.005 mass % or more and 0.03 mass % or less. Therefore, a Zr—P compound or a Cr—Zr—P compound is formed by reacting with Zr and Cr. The Zr—P compound and the Cr—Zr—P compound are stable even at high temperature. Therefore, even in the case of being used under high-temperature conditions, it is possible to prevent local decrease in strength and improvement of conductive property (thermal conductivity) from occurring. In addition, a crystal grain size can be prevented from becoming coarse, and high-temperature strength can be improved.

Furthermore, the Zr content [Zr] (mass %) and the P content [P] (mass %) have the relationship of [Zr]/[P]≥5. Therefore, even when the Zr—P compound or the Cr—Zr—P compound is formed, the number of the Cu—Zr precipitates contributing to strength improvement is secured, and strength improvement can be achieved.

In addition, the Sn content [Sn] (mass %) and P content [P] (mass %) have the relationship of [Sn]/[P]≤5. Therefore, the decrease in electrical conductivity due to a solid solution of Sn can be compensated for by an increase in electrical conductivity due to the formation of the Zr—P compound or the Cr—Zr—P compound, and excellent conductive property (thermal conductivity) can be secured.

The casting mold material and the copper alloy material further include Si in an amount of 0.005 mass % or more and 0.03 mass % or less. Therefore, strength can be further improved by solid solution strengthening due to dissolving of Si in the copper matrix. In addition, since Si is not contained excessively, it is possible to prevent electrical conductivity from decreasing.

In the casting mold material and the copper alloy material, the total content of elements of Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti, which are impurity elements, is limited to 0.03 mass % or less. Therefore, it is possible to prevent a conductive property (thermal conductivity) from decreasing.

In the casting mold material, since the electrical conductivity is higher than 70% IACS, Cr precipitates and Zr precipitates are sufficiently dispersed, and the Zr—P compound or the Cr—Zr—P compound is formed. Accordingly, even in the case of being used under high-temperature conditions, it is possible to prevent local decrease in strength and improvement of conductive property (thermal conductivity) from occurring. In addition, crystal grain size can be prevented from becoming coarse, and high-temperature strength can be improved.

In the casting mold material, since the Vickers hardness is 115 Hv or more, sufficient hardness is obtained, and it is possible to prevent deformation from occurring and use the material favorably as a casting mold material.

In the casting mold material, since the average crystal grain size after performing the heat treatment at 1000° C. for 30 minutes is set to 100 μm or smaller, even when used under high-temperature conditions, the crystal grain size is prevented from becoming coarse, and a decrease in strength can be prevented from occurring. In addition, propagation speed of a fracture can be suppressed and a large breakage due to thermal stress or the like can be prevented from occurring.

In the copper alloy material, since electrical conductivity after performing a solution treatment at 1015° C. for 1.5 hours and then performing an aging treatment at 475° C. for 3 hours is higher than 70% IACS, Cr precipitates and Zr precipitates are sufficiently dispersed, and the Zr—P compound or the Cr—Zr—P compound is formed. Accordingly, even in the case of using the copper alloy material under high-temperature conditions, it is possible to prevent local decrease in strength and improvement of conductive property (thermal conductivity) from occurring. In addition, crystal grain size can be prevented from becoming coarse, and high-temperature strength can be improved.

Hereinbefore, a description has been given of the embodiments of the present invention. However, the present invention is not limited thereto, and approximate modifications can be made in a range not departing from the technical spirit of the invention.

For example, a method of producing the casting mold material is not limited to the present embodiment, and the casting mold material may be produced by another production method. For example, a continuous casting apparatus may be used in the melt casting step.

Examples

Hereinafter, the results of experiments carried out to confirm the effects of the present invention will be described.

A copper raw material formed of oxygen-free copper with a copper purity of 99.99 mass % or higher was prepared and charged into a carbon crucible and melted using a vacuum melting furnace (vacuum degree 10⁻² Pa or lower) to obtain molten copper. Other elements were added to the obtained molten copper to have the component compositions shown in Table 1, and after kept for 5 minutes, the molten copper alloy was poured into a cast iron mold to obtain an ingot. The size of the ingot was approximately 80 mm wide, approximately 50 mm thick, and approximately 130 mm long.

For the additive elements, a Cr raw material with a purity of 99.99 mass % or higher, a Zr raw material with a purity of 99.95 mass % or higher, and a Sn material with a purity of 99.99 mass % or higher were used. P was used as a mother alloy with Cu.

Next, homogenization treatment was performed in an air atmosphere under conditions of 1000° C. for 1 hour, and then hot rolling was performed. A rolling reduction during hot rolling was set to 80%, and a hot-rolled material having a width of approximately 100 mm×thickness of approximately 10 mm×length of approximately 520 mm was obtained. Using the hot-rolled material, solution treatment was performed under conditions of 1000° C. for 1.5 hours, and then water-cooled.

Next, aging treatment was performed under conditions of 525 (±15)° C. for 3 hours. Accordingly, a casting mold material was obtained.

The obtained casting mold material was evaluated for a component composition, Vickers hardness (rolled surface), and electrical conductivity. In addition, an average crystal grain size after being kept at 1000° C. for 30 minutes was measured. Evaluation results are shown in Table 1.

(Component Composition)

The component composition of the obtained casting mold material was measured by ICP-MS analysis. Measurement results are shown in Table 1.

(Electrical conductivity)

Using SIGMA TEST D2.068 (probe diameter φ: 6 mm) manufactured by Foerster Japan Limited, the center of a cross section of a 10×15 mm sample was measured three times, and an average value thereof was determined.

(Vickers Hardness)

According to JIS Z 2244, Vickers hardness was measured using a Vickers hardness tester (manufactured by Akashi Seisakusho, Ltd.) at nine locations on the test piece as shown in FIG. 2, and an average value of seven measured values excluding the maximum and minimum values was determined.

(Average Crystal Grain Size)

A 10 mm×15 mm test piece was collected for observation from the plate width center, and a surface thereof in a rolling direction was polished and then microetched. The microstructure was observed using an optical microscope, the crystal grain sizes were measured based on JIS H 0501: 1986 (cutting method), and the average crystal grain size was calculated.

TABLE 1 Evaluation Average Composition crystal Total content grain size Cr Zr Sn P Si of Mg, Al, Fe, Electrical after heat (mass (mass (mass (mass (mass Ni, Zn, Mn, Co, conductivity Hardness treatment %) %) %) %) %) and Ti (mass %) Cu [Zr]/[P] [Sn]/[P] (% IACS) (Hv) (μm) Present 1 0.45 0.13  0.005 0.005 — <0.01 Balance 26.0 1.0 85 120 57 Example 2 0.45 0.13 0.03 0.006 — <0.01 Balance 21.7 5.0 72 152 68 3 0.45 0.13 0.02 0.008 0.20 <0.01 Balance 16.3 2.5 75 143 67 4 0.55 0.15 0.04 0.030 — <0.02 Balance 5.0 1.3 80 130 15 5 0.50 0.15 0.03 0.010 0.20 <0.01 Balance 15.0 3.0 72 148 47 6 0.45 0.13 0.02 0.008 — 0.04 Balance 16.3 2.5 70 142 54 Comparative 1 0.45 0.13 0.08 — — <0.01 Balance — — 69 154 91 Example 2 0.45 0.13 — 0.060 — <0.01 Balance 2.2 — 86 112 13 3 0.45 0.07 0.02 0.020 — <0.01 Balance 3.5 1.0 87 113 24 4 0.45 0.13 0.04 0.005 — <0.02 Balance 26.0 8.0 65 140 77

In Comparative Example 1, in which P was not added, the electrical conductivity was 69% IACS. It is presumed that this is because a compound containing Zr and P was not formed, and Zr was dissolved in the matrix.

In Comparative Example 2, in which Sn was not added, the Vickers hardness was 112 Hv. It is presumed that this is because the strength improvement by solid solution hardening of Sn was not achieved.

In Comparative Example 3 in which [Zr]/[P] was 3.5, the Vickers hardness was 113 Hv. It is presumed that this is because the number of Cu—Zr precipitates contributing to strength improvement could not be secured.

In Comparative Example 4 in which [Sn]/[P] was 8.0, the electrical conductivity was 65% IACS. It is presumed that this is because the decrease in electrical conductivity due to solid solution of Sn cannot be compensated for by an increase in electrical conductivity due to the formation of the Zr—P compound or the Cr—Zr—P compound.

On the other hand, it was confirmed that Present Examples 1 to 6, in which the contents of Cr, Zr, Sn, P, and Si, [Zr]/[P], [Sn]/[P] are within the ranges of the present invention, are particularly suitable as a casting mold material because the electrical conductivity is 70% IACS or higher and a Vickers hardness is 115 Hv or more.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide a casting mold material which is excellent in high-temperature strength, prevents local decrease in strength and improvement of conductive property (thermal conductivity) from occurring even in the case of being used under high-temperature conditions, and is capable of stably performing casting and a copper alloy material suitable for the casting mold material. 

1. A casting mold material used when casting a metal material, comprising: Cr within a range of 0.3 mass % or more and 0.7 mass % or less; Zr within a range of 0.025 mass % or more and 0.15 mass % or less; Sn within a range of 0.005 mass % or more and 0.04 mass % or less; P within a range of 0.005 mass % or more and 0.03 mass % or less; and a balance consisting of Cu and inevitable impurities, wherein a Zr content [Zr] (mass %) and a P content [P] (mass %) have a relationship of [Zr]/[P]≥5, and a Sn content [Sn] (mass %) and a P content [P] (mass %) have a relationship of [Sn]/[P]≤5.
 2. The casting mold material according to claim 1, further comprising: Si within a range of 0.005 mass % or more and 0.03 mass % or less.
 3. The casting mold material according to claim 1, wherein a total content of Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti is 0.03 mass % or less.
 4. The casting mold material according to claim 1, wherein electrical conductivity is higher than 70% IACS.
 5. The casting mold material according to claim 1, wherein Vickers hardness is 115 Hv or more.
 6. The casting mold material according to claim 1, wherein an average crystal grain size after performing heat treatment at 1000° C. for 30 minutes is 100 μm or smaller.
 7. A copper alloy material comprising: Cr within a range of 0.3 mass % or more and 0.7 mass % or less; Zr within a range of 0.025 mass % or more and 0.15 mass % or less; Sn within a range of 0.005 mass % or more and 0.04 mass % or less; P within a range of 0.005 mass % or more and 0.03 mass % or less; and a balance consisting of Cu and inevitable impurities, wherein a Zr content [Zr] (mass %) and a P content [P] (mass %) have a relationship of [Zr]/[P]≥5, a Sn content [Sn] (mass %) and a P content [P] (mass %) have a relationship of [Sn]/[P]≤5, and electrical conductivity after performing a solution treatment at 1015° C. for 1.5 hours and then performing an aging treatment at 475° C. for 3 hours is higher than 70% IACS.
 8. The copper alloy material according to claim 7, further comprising: Si within a range of 0.005 mass % or more and 0.03 mass % or less.
 9. The copper alloy material according to claim 7, wherein a total content of elements of Mg, Al, Fe, Ni, Zn, Mn, Co, and Ti is 0.03 mass % or less. 